One of West Yorkshire Police’s most senior murder detectives has been placed on restricted duties after allegedly using racist language at a work Christmas party.

Detective Chief Inspector Elizabeth Belton has been made the subject of a misconduct investigation by the force’s Professional Standards Department after an allegation was made that she used “inappropriate language”.

It is understood that the alleged racist remarks were made at a Christmas party held by the force’s Homicide and Major Enquiry Team.

West Yorkshire Police said in a statement today: “An allegation has been made in relation to a serving West Yorkshire Police officer using inappropriate language.

“The officer was put on restricted duties following this allegation being made and an investigation is ongoing by the Force’s Professional Standards Department.”

West Yorkshire Police’s Homicide and Major Enquiry Team is the unit responsible for investigating some of the region’s most high profile cases.

Ms Belton is leading the new enquiry into the historic murder of Wakefield teenager Elsie Frost in 1965, as well as a probe into the murder of 27-year-old Nicholas Dean Williams, who was found murdered in his home in Stanley near Wakefield.

A force spokeswoman declined to comment on the specifics of the case, but said that in general when an officer is placed on restricted duties, any duties they are carrying out will be taken over by another officer.

West Yorkshire’s branch of the Police Federation, which represents officers from police constable through to chief inspector, declined to comment on the case.

The incident is not the first time Ms Belton, the former head of North East Leeds CID, has been the subject of an internal investigation.

In 2012, an enquiry was launched after she and a colleague, Chief Superintendent Ian Whitehouse, were confronted by one of their partners at a gym in Killingbeck police station in Leeds.

Chief Superintendent Ian Whitehouse and Ms Belton’s partner, Sergeant Chris Beddis, are understood to have been involved in a heated exchange during the incident. West Yorkshire Police said all three officers were off duty at the time.

The force said in a statement: “We are aware of an incident involving two off-duty officers in a gym run by the local sports and social club in Killingbeck Police Station when they were confronted by one of the officers’ partners.

“The officers involved do not work together and what they do in their own time off duty is not a matter for the force unless it compromises our own high standards of professional behaviour.”